A Mild Alkaline Hydrothermal Etchant for MBene Exfoliation

MoBene (the boride equivalent of MXenes) has been a synthetic challenge because borides degrade in common etching media. Inspired by the intercalation of lithium ions into AlOOH, we hypothesized that a hydrothermal route enables lithium ions to intercalate the aluminum layer of MoAlB and further separate the MoB sheet apart. Here, MoBene is first synthesized through a mild hydrothermal etching method with dilute lithium hydroxide. X-ray diffraction showed a peak at 8.9°, confirming an exfoliated layered structure, and the presence of MoBene sheets is further confirmed by SEM. Intriguingly, MoBene sheets, as the crystallographic subunit of the parent monoboride structure, can be readily restacked to crystalline MoB by heating in a mildly reducing atmosphere, which further confirmed the crystallinity of our product and demonstrated the ready synthesis of refractory materials at low temperature. The exfoliated MoBene product has chelating hydroxyl functional groups and can adsorb 318 mg/g of lead in water.